This article is written for someone who just wants to give it a try anyway.
If youre interested in details, please read the official docs.
The application that youre going to make from now, inserts 1 user with 2 breads every time you start the app. :)

1. Add this line to the project level build.gradle.

classpath 'io.realm:realm-gradle-plugin:3.1.4'

2. Add this line to the top of the application level build.gradle.

apply plugin: 'realm-android'

3. Refresh gradle dependencies.

4. Configure a Realm in MyApplication.java.

5. Add MyApplication to application tag in the apps AndroidManifest.xml.

<applicationandroid:name=".MyApplication"></application>

6. Create a User class.
You can mark a field as a primary key with @PrimaryKey.
Other annotation types summary is HERE.

7. Create a Bread class.

8. Write insert function in MainActivity.java.
As I mentioned before, this app inserts 1 user and 2 breads into Realm DB when onCreate() is called.
There is an auto-incrementing ID helper but its not recommended when you:

1) Create Realm Objects in multiple processes. 2) Want to share the Realm between multiple devices at some point in the future.

Here is an example of auto-Increment ID for creating objects across processes.

9. Copy database to somewhere accessible.
Realm provides a Mac app to edit and read your database.
Currently, this app doesnt support accessing database directly.
You have to copy it from emulator or device to somewhere accessible.